1. Radiator: Check the radiator for any cracks or leaks. If the radiator is damaged, it will need to be replaced.
2. Radiator hoses: Inspect the radiator hoses for any cracks or leaks. If the hoses are damaged, they will need to be replaced.
3. Water pump: Check the water pump for any leaks. If the water pump is damaged, it will need to be replaced.
4. Cylinder head gasket: A blown cylinder head gasket can also cause antifreeze to leak. If the cylinder head gasket is damaged, it will need to be replaced.
5. Heater Core: The heater core is located behind the dashboard and can also leak. If the heater core is leaking, it will need to be replaced.
Since you haven't found any antifreeze on the ground, it's possible that the leak is internal. If you can't find the leak yourself, you can take your Blazer to a mechanic for further diagnosis.